Fixture for handling and attaching conductive spheres to a substrate

Abstract

Methods for soldering a ball grid array (BGA) integrated circuit package to a printed circuit board. One method includes the steps of applying a solder flux to the conductive surface pads of a printed circuit board and capturing a plurality of solder balls with a separate fixture. The fixture is then placed onto the printed circuit board and the solder balls are released onto the conductive surface pads. The fixture is removed and an integrated circuit package is placed onto the solder balls. Solder flux may be applied to the bottom of the package to adhere the package to the balls. The solder balls are then reflowed to attach the package to the board. The flux provides a bonding agent which maintains the position of the solder balls and package while the solder is being reflowed. Another method includes the step of placing a fixture adjacent to the integrated circuit package so that a plurality of openings in the fixture are aligned with surface pads located on the bottom surface of the package. Solder balls are then placed into the fixture holes, adjacent to the surface pads of the package. The solder is then reflowed and the fixture is removed so that the package and solder balls can be subsequently soldered to a printed circuit board.

What is claimed is: 
     
       1. A fixture for attaching a solder ball to a conductive pad located on a bottom surface of an integrated circuit package, comprising: a fixture housing which can be placed onto the bottom surface of the integrated circuit package, said fixture housing having a tapered aperture that is aligned with the conductive pad and which maintains a position of a solder ball placed onto the conductive pad while the solder ball is reflowed.   
     
     
       2. The fixture as recited in claim 1, wherein said fixture has a coefficient of thermal expansion that is approximately equal to a coefficient of thermal expansion of the integrated circuit package.